1. Field of the Invention
The present invention relates to a fuel processor, and more particularly to an air-cooling plate type preferential oxidation reactor capable of effectively removing carbon monoxide contained in reformed gas.
2. Description of Related Art
A fuel processor is a processor or system, which produces hydrogen from fuel. The fuel processor includes an apparatus for producing reformed gas by reforming fuel gas, and an apparatus for removing sulfur and/or carbon monoxide contained in the reformed gas. Hydrogen produced by the fuel processor is used for a power generation system such as a fuel cell etc.
The fuel cell, which is a non-polluting power supplying device, has been spotlighted as one of the clean energy power generation systems for the next generation. The power generation system using the fuel cell is used for an independent power generator of large sized buildings, power supplier of electric cars, portable power supplier etc., and it has the advantage of being capable of using various fuel such as natural gas, methanol, petroleum, liquefied petroleum gas (LPG), di-methyl ether (DME), coal, waste gas etc. The fuel cells are basically operated based on the same principle, and according to types of electrolyte used in the fuel cells, fuel cells can be categorized as phosphoric acid, alkaline, polymer electrolyte, direct methanol, and solid oxide fuel cells.
Among the above mentioned fuel cells, a polymer electrolyte membrane fuel cell (PEMFC) using polymer as electrolyte has no risk of the corrosion or evaporation by the electrolyte, and obtains high current density per unit area. Further, because the polymer electrolyte membrane fuel cell (PEMFC) has the advantage of a remarkably high output and a low operating temperature over other fuel cells, it has actively been developed for being applicable to a mobile power source for a portable electronic equipment, a transportable power source such as a power source for automobile, a distributed power source such as a stationary power plant used in a house and a public building, etc.
The polymer electrolyte fuel cell produces electric energy by an electrochemical reaction between hydrogen supplied to an anode and oxygen supplied to a cathode. Pure hydrogen, hydrogen generated from a metallic alloy that is capable of producing hydrogen gas, or hydrogen contained in reformed gas from fossil fuel can be used for the polymer electrolyte fuel cell. Pure oxygen or oxygen contained in the air can be used for the polymer electrolyte fuel cell. However, the pure oxygen or the metallic alloy for hydrogen storage is difficult to use because of high cost, which is caused by difficulties of manufacture, storage, and transportation. Accordingly, hydrogen-rich reformed gas that is generated from a fuel reformer is commonly used for hydrogen fuel of the fuel cell.
The fuel reformer includes a steam reforming (SR) reactor producing hydrogen-rich reformed gas by a reaction between fuel and steam, a partial oxidation (POX) reactor producing hydrogen-rich reformed gas by oxidizing fuel, and a reactor which combines the steam reforming reaction and the partial oxidation reaction. A carbon monoxide reducer includes a water gas shift (WGS) reactor and a preferential oxidation (PROX) reactor.
In general the PROX reactor removes carbon monoxide from reformed gas by using oxidizer, which has high carbon monoxide selectivity, after the reformed gas is mixed with air. Temperature of the reactor may be maintained in the range of 130° C. to 250° C., so that selectivity of an oxidation reaction is excellent and speed of the reaction is fast. However, it is difficult to maintain the range of temperature in the PROX reaction, because the PROX reaction is an exothermic reaction generating heat. Also, it is difficult to maintain uniform reaction temperature in the PROX reactor, because of temperature difference that is generated along the direction of flow of the reformed gas. Accordingly, it is difficult to uniformly control the oxidation reaction in the PROX reactor. Therefore it is necessary to prevent temperature variation and to maintain the temperature in a predetermined range. Otherwise, performance deteriorates depending on the range of temperature in the PROX reactor.
If a high temperature hot spot is generated in a catalyst layer of the PROX reactor, activity of the catalyst positioned in the hot spot deteriorates rapidly, and the hot spot spreads over the catalyst layer. Thereby activity of the catalysts in the reactor deteriorates rapidly.